1. Field of the Invention
The present invention relates to a new and improved unitary, rigid, drop-in type filter for use in a high temperature, high pressure application in a pyrotechnic airbag inflator. More particularly, the filter is particularly designed to withstand the high temperature and high pressures encountered from contact with gas generated in a pyrotechnic airbag inflator from gas generating material such as sodium azide wafers. The filter functions to cool the hot gases before they reach the airbag and serves to eliminate and trap particulates and residues generated during ignition so that they do not enter the airbag and contaminate the vehicle.
2. Background of the Prior Art
In prior pyrotechnic airbag inflators, wire or metal mesh or screen has been used to filter the gaseous flow emanating from the ignition of the pyrotechnic materials of an airbag inflator, before the gases enter the airbag. Japanese unexamined Patent Publication No. 50-48797 discloses an air permeable trap or filter of granules or particles used to screen or filter gaseous flow from an airbag inflator before the gas enters the airbag.
A major concern in pyrotechnic type airbag inflators is that the expanding gas generated for inflation of an airbag is so high in temperature that burning of the airbag or injury to a passenger occurs when the airbag is inflated. Sometimes, pyrotechnic material is ignited to generate high temperature gas which contains impurities such as molten or gaseous metals and oxides which are toxic and cause damage to the human body.